Has anyone found any more details on this v-max head setup? Even the Japanese sites have very little info. One does refer to the engine as "hand carved" (thanks, google translate), which I think supports Carrotsnax's theory that the cylinder portion of the engine is custom made to match the 360 below and the v-max above.

I more-or-less have the resources and the skills to machine such a thing, but what I'm not sure of is how much I would gain over my stock n600 sohc. Any thoughts on the actual benefits of this sort of upgrade?

It almost makes sense, although I'm baffled by the talk of an added 5th gear. To augment VWDMC16's summary, below are better translations of the two summaries on the page itself (one at the beginning and one at the end):

"In the beginning tried to make N600 engine a DOHC engine including a missing 5th gear. Then it's said that it's good for nothing, and I'm going to put 600 cranks in 5th gear of GS.

● N600 crank is changed to type 180-degree.
● A stroke is long, so about 20 mm of cylinder is raised.
● Because a N600 primary is used, so a driven sprocket became big and a chain also became thick.
● A cover in a driven place was reformed newly including a spacer in the left crank side cover case.
● A tensioner is also manufactured newly.
● A cylinder also manufactured
● The sentence muffler which became expensive newly.
● It's cold for winter, so a duct is also manufactured."

Engine details, second versionReinforcement piston pin It's made newly 10.2mm of inside diameter.
The crank condition lot part 1 mm was set off and an offset of a piston was lost. I make a mistake in pin height and put a shim of 1.5mm under the cylinder."

Honestly, most of the rest of the text on the page is a semi-imaginary dialogue between "Mr. I" and "The Chairman" in which they bicker about whether the build can be done. At least there are lots of photos. I believe that there is almost enough information now to do this, if the doer has a good sense of how to build an engine.

VWDMC16, I thought you gave up on this in May, but does this mean that it is still on your mind? Are you moving forward or just curious?

I have also seen a pic of a 72 z600 gss. It looks like a twin carb to on the early motors with a orange air box I can't really tell its a small pic but the outher s might be a type o. Ill post up the pic later today.

Yes as said the last car is one of the later Honda Life based Watercooled Honda Z360 that replaced the Z360 air-cooled (with a signifigantly revised front structure & engine/transmission layout: 80mm longer wheelbase -same length).

The 600 engine would be VERY rare in Japan since they didn't fit in the regular 360cc Kei-car tax category so some of their sites talk of importing these engines or complete cars from the US. with American spec. cars sometimes appearing for sale there.

So the Z GSS with a 5-speed g/box, twin carbs & 'Upgraded brakes' mentioned would have been a 360cc car with significant engine/transmission differences possibly making the fitment of those parts into a 600 bottom end difficult.
The Standard Z600 disc brakes would have been an upgrade since most Z360 only came with drum brakes all round. I'm not even sure if disc brakes were offered on the later watercooled Z360life cars since I guess they would mostly have been developed for the export oriented Z600